Grooved reflector lamp



Dec. 27, 1966 M. A. CHERNIN GROOVED REFLECTOR LAMP Filed Nov. 18, 1963 Invervtov: Mgvon A Chernin b9 6 His A t ovneg United States Patent Ofiflce 3,295, 3 Patented Dec. 27, 1966 This invention relates to a reflector fluorescent lamp of novel construction for producing a concentrated beam of light of higher output and greater uniformity than heretofore possible.

A reflector fluorescent lamp is a form of fluorescent lamp which is provided with a reflective coating extending around a portion of the periphery of the lamp in such manner as to leave a slot or window extending lengthwise. The window may be phosphor-coated or clear. When the reflective coating extends around a major portion of the periphery and a clear window is provided, a concentrated beam of light of relatively narrow angular spread is emitted and such reflector lamps are sometimes termed aperture lamps. Reflector lamps are useful where accurate control of the beam pattern from a long linear light source is required. They are particularly useful for such applications as photo reproduction and reprographic processes in general.

The object of the invention is to provide a novel reflector fluorescent lamp structure which achieves a higher light output and window brightness than heretofore possible while yet maintaining accurate control of the angular spread of the light beam.

It is well-known that in configurated fluorescent lamps having short re-entrant sections of groove or indentations alternating on opposite sides as in the type designated commercially PG17, the highest brightness is found in the bottom of these indentations. However the angular spread of the light from the groove sections is too great for the applications intended for a reflector lamp. I have foundhowever, that the high groove brightness characteristic of configurated lamps may be utilized to advantage in a reflector or aperture lamp construction by providing a single longitudinally extending groove and placing the clear slot or window in the wall of the lamp opposite the groove. What is seen through the window is the inside of the bottom of the groove. By this means, an increase in light output and window brightness of as much as 40% is achieved by comparison with a lamp of the same physical dimensions but lacking the longitudinally extending groove, while yet achieving the desired light control and beam intensity.

For further objects and advantages and for a better understanding of the invention, attention is now directed to the following description of a preferred embodiment to be read in conjunction with the accompanying drawing. The features of the invention believed to be novel will be more particularly pointed out in the appended claims.

In the drawing:

FIG. 1 shows the window side of a grooved reflector lamp embodying the invention, a central section being cut away for convenience of illustration.

FIG. 2 is a similar view of the lamp looking at the grooved side.

FIG. 3 is a cross-sectional view through the lamp.

The illustrated lamp comprises an elongated glass tube 1 forming the envelope into whose ends are sealed a pair of electrodes 2, 2. The electrodes, which are schematically illustrated only, may by way of example be of the thermionic type, each comprising a tungsten filament coated with electron emitting material consisting chiefly of alkaline earth oxides and supported across inleads 3, 4 sealed through the usual stem press and connected to the terminal pins 5, 6 of a base 7. The envelope is provided on one side with a longitudinally extending transversely reentrant portion or groove 8. In cross section, except for the cylindrical ends, the lamp is generally kidney-shaped as illustrated in FIG. 3, following the teachings of Patents 2,915,664, Lemmers, Tubular Electric Lamp, and 2,950,- 410, Lemmers et al., Multiple Groove Discharge Lamp. As illustrated, a single groove extends continuously along one side of the lamp rather than short sections of groove alternating on opposite sides. As explained in the aforementioned patents, the grooved conflguration providesdecided advantages in regards to electrical loading, mercury vapor pressure control and light output at the same time as it achieves a strong vitreous structure resistant to implosion.

The envelope contains a filling of inert gas, for instance argon or a mixture of argon with another rare gas such as neon or helium at a pressure of a few torr (millimeters of mercury) together with sufficient mercury to provide a vapor pressure of a few microns in operation. The illustrated example may be described as a grooved 18T8 size, that is the envelope has an overall nominal length of 18" and diameter of 1 when the groove is disregarded.

As best seen in FIG. 3, a reflective coating 9 is applied to the inside surface of the glass envelope 1 over the major portion of the periphery and a phosphor coating 11 is applied thereover. The reflective coating is desirably an efficient reflector of visible light in preference to being an efficient reflector of ultraviolet 25 37 A. radiation, and the fluorescent phosphor layer is proportioned to absorb substantially the entire ultraviolet radiation produced by the discharge. A preferred material for the reflector layer is titanium dioxide having a particle size less than one micron, for instance centering on about 0.3 micron which is about half the median wavelength of the visible spec trum. An alternative reflective material is zirconia.

A suitable method for applying the reflective coating is the upflush method wherein the titania is applied as a suspension in an organic binder which is drawn up into the tube supported vertically, and then allowed to drain out. Thereafter the tube is lehred in order to decompose and drive out the organic binder, leaving only a thin layer of titania adhering to the glass wall. The phosphor coating 11, consisting for example of calcium halophosphate activated with manganese and antimony or any other suitable fluorescent lamp phosphor, is then applied over the reflective coating. The phosphor may be applied as a suspension in a water soluble binder or alternatively in an organic binder such as previously mentioned. The upflush method may again be used and preferably the suspension is twice drawn up into the tube and allowed to drain, the tube being reversed end for end after the first occurrence in order to compensate for drainage characteristics and obtain an even thickness of coating over the entire length. The envelope is then lehred again and thereafter both coatings are scraped out or brushed off to provide a clear window or slot 12 on the side opposite the groove. Alternatively, both reflective and phosphor coatings may be applied and then lehred in one operation. Other methods of forming the window may of course be used. For a concentrated beam, a relatively narrow window is provided subtending no more than the groove; a 30 window is illustrated in the drawing.

In an aperture fluorescent lamp having a clear slot or window, it is desirable to use a glass which is more resistant to ultraviolet radiation and mercury vapor attack than the usual soda lime glass. Suitable glasses for this purpose are well-known, one which is commercially available going under the designation Corning 0088 and being characterized by the presence of a percentage of alumina in the glass mixture. Alternatively, one may have a phosphor-coated window, that is the slot or window is provided in the reflective coating only and the phosphor coating is thereafter applied over the entire interior surface.

In the illustrated lamp, the groove 8 extends less than the entire length of the envelope and this conveniently results in cylindrical ends for attachment of the bases 7. The window or slot 12 likewise extends less than the entire length of the tube and may suitably be made coextensive with the groove or shorter than the groove. There is then obtained the eifect described in copending application Serial No. 294,536, filed July 12, 1963, of Myron A. Chernin and Elton T. Leppelmeier, entitled Reflector Fluorescent Lamp, and assigned to the same assignee as the present invention, whereby the light output about the ends of the window is reenforced and a substantially uniform brightness is obtained from end to end of the window.

In actual tests of a sample lamp constructed as illustrated in the drawing and described herein, a 22% increase in directional brightness, that is in brightness looking into the slot, and a 42% increase in total spherical lumens was obtained over a round aperture lamp of the same overall dimensions when the lamps were operated at the same current.

While a certain specific embodiment of the invention has been illustrated and described in detail, it is intended as exemplary only. Other sizes and ratings are of course equally feasible. The scope of the invention is to be determined by the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A reflector fluorescent lamp comprising a tubular elongated vitreous envelope having electrodes sealed into opposite ends and containing an ionizable medium including mercury vapor and an inert gas at a low pressure, a reflective coating and a phosphor coating thereover applied to the inside surface of said envelope, said envelope having a re-entrant groove extending continuously along one side thereof, said reflective coating extending over the entire interior of said envelope except for a relatively narrow window extending lengthwise in the wall directly opposite said groove.

2. A reflector fluorescent lamp comprising a tubular elongated vitreous envelope having electrodes sealed into opposite ends and containing an ionizable medium including mercury vapor and an inert gas at a 10W pressure, a reflective coating and a phosphor coating thereover applied to the inside surface of said envelope, said envelope having a re-entrant groove extending continuous- 1y along one side thereof, said coatings extending over the entire interior of said envelope except for a relatively narrow window extending lengthwise in the wall directly opposite said groove.

3. A reflector fluorescent lamp comprising a tubular elongated vitreous envelope having electrodes sealed into opposite ends and containing an ioniza'ble medium including mercury vapor and an inert gas at a low pressure, a reflective coating and a phosphor coating thereover applied to the inside surface of said envelope, said envelope having a re-entrant groove extending continuously along one side thereof except for short cylindrical end sections, said coatings extending over the entire interior of said envelope except for a relatively narrow window extending lengthwise in the wall directly opposite said groove and not exceeding said groove in longitudinal extent.

4. A reflector fluorescent lamp comprising a tubular elongated vitreous envelope having electrodes sealed into opposite ends and containing an ionizable medium including mercury vapor and an inert gas at a low pressure, a reflective coating and a phosphor coating thereover ap plied to the inside surface of said envelope, said envelope having a re-entrant groove extending continuously along one side thereof except for short cylindrical end sections, said coatings extending over the entire interior of said envelope except for a relatively narrow window extending lengthwise in the wall directly opposite said groove and having a width such that the window subtends only the bottom of the groove, said window not exceeding said groove in longitudinal extent.

References Cited by the Examiner UNITED STATES PATENTS 2,757,300 7/1956 Laidig 313-113 2,859,369 11/1958 Williams et al 3l31l3 X 2,915,664 12/1959 Lemmers 3 l3l09 3,174,067 3/1965 Bahrs 313'l 13 X 3,225,241 12/1965 Spencer et al 3l3-113 X JOHN W. HUCKERT, Primary Examiner.

R. POLISSACK, Assistant Examiner. 

1. A REFLECTOR FLUORESCENT LAMP COMPRISING A TUBULAR ELONGATED VITREOUS ENVELOPE HAVING ELECTRODES SEALED INTO OPPOSITE ENDS AND CONTAINING AN IONIZABLE MEDIUM INCLUDING MERCURY VAPOR AND AN INERT GAS AT A LOW PRESSURE, A REFLECTIVE COATING AND A PHOSPHOR COATING THEREOVER APPLIED TO THE INSIDE SURFACE OF SAID ENVELOPE, SAID ENVELOPE HAVING A RE-ENTRANT GROOVE EXTENDING CONTINUOUSLY ALONG ONE SIDE THEREOF, SAID REFLECTIVE COATING EXTENDING OVER THE ENTIRE INTERIOR OF SAID ENVELOPE EXCEPT FOR A RELATIVELY NARROW WINDOW EXTENDING LENGHTWISE IN THE WALL DIRECTLY OPPOSITE SAID GROOVE. 